Recent ski boots comprise each a shell formed of a hard plastic material, and an inner boot for holding a skier's foot within the shell in close contact condition without any gaps. In order to favorably hold the foot in the ski boot for the improved operability of a ski plate while skiing, a fastening mechanism is used to fasten an upper portion of the shell embracing the lower leg end, or fixedly hold the instep, thereby ensuring skiers to enjoy a comfortable fit at lower ends of their legs.
Heretofore, ski boots of this type are disclosed in Japanese Patent Publication No. 55-7242 (1980) by way of example.
The disclosed ski boot has a shell body which is formed in its rear portion with a cut-out opening extending from an upper end to an ankle part of the shell body. The cut-out opening is capable of spreading, with compatible deformation of the shell body; and a tongue member is disposed in association with the cut-out opening for closing the same from the inside. The tongue member is connected at its lower end to an inner bottom of the shell body through a flexible part, so that when the foot is placed into, and withdrawn from, the boot, the tongue member is tiltable about the flexible part toward the outside of the shell body through the cut-out opening.
With such a ski boot including the shell body provided with the cut-out opening, the skier's foot can be inserted within, and withdrawn from, the boot by spreading the cut-out opening and then tilting the tongue member outwardly.
However, because the shell body is formed of a semi-hard or hard plastic material for the purpose of stably and favorably holding the skier's foot in the boot, a substantial force by the fingers is required to expand and deform the cut-out opening so that feet encased in thick socks may be inserted within, and withdrawn from, the boot with relative ease. If the cut-out opening is not expanded and deformed to the requisite extent, a skier, upon donning the boot, as well as removing the foot therefrom, will necessarily experience pain or discomfort in the instep, ankle, and adjacent zones subjected to the insufficiently expanded opening with the concurrent pressure caused thereby. It is also conceivable to increase the mouth diameter of the shell body for facilitating foot insertion and withdrawal. But this arrangement causes an inadequacy in both the manner in which the lower leg end of the shell body fits, as well as the fastening of such lower leg end, thereby resulting in further problems imparing the edge operation of a ski plate.